Anytime I find something coming in threes within the church, I always assume that it represents the Trinity. My favorite example is:
Holy, Holy, Holy Lord,
God of power and might.
Heaven and earth are full of your glory.
Hosanna in the highest.
Blessed is he who comes in the name of the Lord.
Hosanna in the highest.
I thought that each Holy in the first line represented the Father, the Son, and the Holy Spirit.
As it turns out, according to David Heddle, there is a Hebrew literary device called trishagion (also spelled trisagion) that is “used to denote an extreme form of emphasis. The thing being emphasized is repeated three times.” Trishagions are used sparingly in the Bible. Their overuse would detract from their impact. Bishagions, a word repeated twice for emphasis, are more common.
Therefore, the three Holy’s in the first line above do not necessarily represent the Trinity, but rather it is a super-ultra-mega-emphasis on the holiness of the Lord.
FYI – The latin word tersanctus refers to the word holy (sanctus in latin) repeated three times. Hosanna means a triumphant shout of praise or adoration, usually in reference to the waving of palm leaves when Jesus entered Jerusalem.